JP2009257869A - Physical quantity sensor and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a highly reliable physical quantity sensor capable of reducing manufacturing costs and provide its manufacturing method. <P>SOLUTION: The method for manufacturing physical quantity sensors includes a process for forming a mask having apertures over a semiconductor substrate; a process for forming a plurality of piezoresistive elements by a thermal diffusion method in the semiconductor device exposed by the apertures; a process for removing the mask after the formation of the piezoresistive elements; a process for forming an insulating layer which covers at least part of the piezoresistive elements on the semiconductor substrate; and a process for forming contact holes by forming holes in the insulating layer within the regions of formation of the piezoresistive elements. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a physical quantity sensor for detecting a physical quantity such as acceleration or pressure and a method for manufacturing the same, and more particularly to a sensor of a type using a piezoresistive element as a detection element.

In recent years, a sensor using a piezoresistor as a detection element has been put to practical use as a sensor having a small and simple structure using a MEMS (Micro Electro Mechanical Systems) technology. For example, Patent Document 1 discloses an acceleration sensor using a piezoresistive element as a detection element. The weight body portion is displaced according to the applied acceleration, and the flexible portion is bent according to the displacement. The piezoresistive element formed in the flexible part changes the resistance value according to the amount of bending (stress) of the flexible part. Then, a voltage is applied to the piezoresistive element, and the acceleration is detected by referring to the voltage value accompanying the resistance change.
JP 2006-98321 A

  In the manufacture of the acceleration sensor in Patent Document 1, the piezoresistive element is formed using an ion implantation method because the impurity implantation amount and implantation depth can be accurately controlled. However, the ion implantation apparatus is very expensive, and an increase in manufacturing cost should be avoided in order to manufacture a sensor at low cost.

  In the ion implantation method, implanted ions having a high energy of several MeV are implanted into the semiconductor layer. For this reason, damage (crystal defects) occurs in the crystal of the semiconductor layer due to the collision of implanted ions. Although crystal defects are recovered to some extent in a later annealing step, they are not completely recovered, and therefore remain in the semiconductor layer. Defects such as the above cause deterioration in the strength of thin-walled flexible parts (including beams or diaphragms) in which piezoresistive elements are arranged, causing a decrease in reliability (Sensors and actuators A 110 (2004) pp.150-156).

  Therefore, in view of the above, an object of the present invention is to provide a physical quantity sensor and a method for manufacturing the same that can reduce manufacturing costs and have high reliability.

  A physical quantity sensor according to the present invention connects a frame part located on an outer peripheral part, a weight part arranged inside the frame part, the frame part and the weight part, and has a thickness larger than that of the frame part. A thin flexible portion; and a plurality of piezoresistive elements formed on the flexible portion for detecting physical quantity fluctuations, wherein a distance between the plurality of piezoresistive elements is made larger than 6 μm. And

  The physical quantity sensor manufacturing method according to the present invention includes a step of forming a mask having an opening on a semiconductor substrate, a step of forming a plurality of piezoresistive elements on the semiconductor substrate exposed by the opening by a thermal diffusion method, After forming the piezoresistive element, removing the mask, forming an insulating layer covering at least a part of the piezoresistive element on the semiconductor substrate, and in a region where the piezoresistive element is formed Forming a contact hole by opening the insulating layer.

According to the present invention, a piezoresistive element is formed using a thermal diffusion method, thereby reducing the manufacturing cost and providing a highly reliable manufacturing method of a physical quantity sensor.
Further, the current leakage between the piezoresistive elements can be reduced by setting the distance between the plurality of piezoresistive elements formed by impurity diffusion to the semiconductor substrate to be larger than 6 μm. By forming the groove in the semiconductor layer between the plurality of piezoresistive elements, current leakage can be further reduced. Therefore, a highly reliable physical quantity sensor can be provided.

A semiconductor triaxial acceleration sensor according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is an overall perspective view of an acceleration sensor according to the present invention.
As shown in FIG. 1, the acceleration sensor 1 is a substantially rectangular parallelepiped, and includes a sensor main body 2 made of a semiconductor substrate and a support substrate 3 made of glass. For the sake of explanation, in the figure, two axes (X axis and Y axis) perpendicular to the plane of the acceleration sensor are set, and a direction perpendicular to the two axes is defined as the Z axis. The sensor body 2 is composed of an SOI (Silicon On Insulator) substrate 110, and is formed by sequentially laminating a silicon film 120, a silicon oxide film 130, and a silicon substrate 140. A weight body (weight section 142) is arranged in a frame (frame section 121 and frame section 141) having an opening, and the weight body is supported by a flexible beam (flexible section 123). ing. The support substrate 3 has a function as a pedestal for supporting the sensor body 2 and a function as a stopper substrate for restricting excessive displacement of the weight body in the downward direction (Z-axis negative direction). Note that when the sensor body 2 is directly mounted on a package substrate (not shown), the support substrate 3 is not necessarily required. In addition to glass, the support substrate 2 can be made of silicon, an insulating resin plate, a metal plate, or the like.

FIG. 2 is an exploded perspective view of the acceleration sensor. The silicon film 120 includes a fixed frame portion 121 (the upper portion of the frame), a weight joint portion 122 disposed inside the frame portion 121, and two pairs (four in total) that connect the frame portion 121 and the weight joint portion 122. The flexible part 123 is provided. The frame portion 121, the weight joint portion 122, and the flexible portion 123 are defined by the opening 124. The frame part 121 is joined to the frame part 141 (the lower part of the frame) via the silicon oxide film 130. Further, the weight joint portion 122 is joined to the weight portion 142 having a substantially crowbar shape in the vertical view through the silicon oxide film 130. The weight part 142 is disposed to be separated from the inside of the frame part 141.
The support substrate 3 is made of, for example, a glass substrate and is bonded to the sensor body 2 by anodic bonding.

FIG. 3 is a plan view and a sectional view of the sensor body. FIG. 3A is a plan view of the sensor main body, and detectors Rx to Rz for detecting accelerations in three axis (XYZ) directions are arranged on the four flexible parts 123. The detection unit is disposed in the vicinity of a region where the flexible part 123 connects to the frame part 121 and the weight joint part 122. In the drawing, detectors Rx1 to Rx4 and Rz1 to Rz4 are arranged in a pair of flexible parts arranged in the direction along the X axis in order to detect acceleration in the X direction and the Z direction. On the other hand, detection parts Ry1 to Ry4 for detecting acceleration in the Y direction are arranged in a pair of flexible parts arranged in the direction along the Y axis. In addition, you may arrange | position the detection parts Rz1-Rz4 to a pair of flexible part arrange | positioned in the direction along the Y-axis.
FIG. 3B is a cross-sectional view of the sensor main body along X-X. The lower surface of the weight portion 142 is made higher than the lower end of the frame portion 141, and the Z-negative direction is caused by a gap between the sensor substrate 142 and the glass substrate 3. It is set so that a certain amount of displacement is possible. FIG. 3C is a cross-sectional view of the sensor body along YY, and the flexible portion 123 is a self-supporting thin film having flexibility.

FIG. 4 is a diagram for explaining the details of the detection unit, and shows a plan view and a cross-sectional view (cross section AA). The detection part R is a piezoresistive element formed by diffusing impurities such as B (boron) and P (phosphorus) in the silicon film 120, and the boundary between the flexible part 123 and the frame part 121 and the flexible part 123. It is arranged near the boundary of the weight junction 122. Although the detection unit R is arranged so as to contact the boundary line connecting the flexible unit 123 and the frame unit 121, the detection unit R may be arranged so as to straddle the boundary line.
The detection unit R is covered with an insulating layer 150 and has a contact hole 151 at a connection point with a wiring (described later). In order to lower the connection resistance, the detection portion exposed by the contact hole 151 may be connected by providing a high concentration diffusion region (impurity diffusion region having a concentration of about 1 to 3 digits higher than that of the detection portion). Note that a total of twelve detection units Rx1 to Rx4, Ry1 to Ry4, and Rz1 to Rz4 are connected in each detection direction to form a bridge circuit. Regarding the bridge circuit connection, Japanese Patent Application Laid-Open No. 2007-322297, which is a patent application of the present applicant, can be referred to. An electrode pad (not shown) for connecting to an external circuit is provided on the frame portion 121, and an extended portion of the wiring 152 is connected to the electrode pad, and an electric signal accompanying acceleration is taken out to the external circuit. .

Next, a method for manufacturing the acceleration sensor according to the first embodiment will be described with reference to FIG. FIG. 7 is a drawing showing the manufacturing method of the first embodiment according to the present invention.
Acceleration sensor manufacturing method according to first embodiment (1) Preparation of SOI substrate (see FIG. 7A)
An SOI substrate 110 in which a silicon film 120, a silicon oxide film 130, and a silicon substrate 140 are stacked is prepared. As described above, the silicon film 120 is a layer constituting the frame part 121, the weight joint part 122, and the flexible part 123. The silicon oxide film 130 is a layer that joins the silicon film 120 and the silicon substrate 140 and functions as an etching stopper layer. The silicon substrate 140 is a layer constituting the frame part 141 and the weight part 142. The SOI substrate 110 is produced by SIMOX or a bonding method. In the SOI substrate 110, the silicon film 120, the silicon oxide film 130, and the silicon substrate 140 have thicknesses of 10 μm, 2 μm, and 600 μm, respectively. A plurality of small acceleration sensors 1 having a square shape of about 1 to 3 mm are arranged on a wafer having a diameter of 150 mm to 300 mm in a multi-faceted manner. As the diameter of the wafer is increased, a large number of sensor chips are manufactured at once, resulting in high productivity. In the future, the diameter of the wafer may be further increased.

(2) Formation of diffusion mask (see FIG. 7B)
A diffusion mask M that is an impurity diffusion mask is formed on the SOI substrate 110 on the silicon film 120 side. As this mask material, for example, a silicon nitride film (Si ₃ N ₄ ), a silicon oxide film (SiO ₂ ), a resist, or the like can be used. Here, after a silicon oxide film is formed on the entire surface of the silicon film 120 by thermal oxidation or plasma CVD (Chemical Vapor Deposition), a silicon nitride film is formed, and a resist pattern (see FIG. An opening corresponding to the detection portion R is formed in the silicon nitride film and the silicon oxide film by wet etching such as RIE (Reactive Ion Etching) and hydrofluoric acid. The diffusion mask M has a two-layer structure of a silicon oxide film and a silicon nitride film from the silicon film 120 side (not particularly distinguished in the drawing). The silicon nitride film is used for preventing diffusion of a diffusing agent, which will be described later.

(3) Formation of detector (see FIG. 7C)
Examples of a method for forming the detection portion (piezoresistive element) by a thermal diffusion method include (a) a coating diffusion method and (b) a vapor phase diffusion method.
(A) Coating / Diffusion Method A diffusing agent containing B (boron) is coated by spin coating or the like. The number of rotations is appropriately adjusted in order to make the diffusing agent have a predetermined thickness. After the application, the dopant (impurities) in the diffusing agent is diffused into the silicon film 120 in an oxygen atmosphere or an air atmosphere in a furnace at a temperature of 650 ° C. to 900 ° C. Thereafter, a high concentration portion of the surface is removed with an acid chemical solution such as hydrofluoric acid, and the surface is oxidized at a temperature of about 800 ° C. to form silicide. After the silicidized portion is removed with an acid chemical solution such as hydrofluoric acid, heat treatment is performed at about 1000 ° C. to a predetermined concentration of 10 ¹⁷ to 10 ¹⁹ (atoms / cm ³ ), and the silicon film 120 is driven. The detection unit R is formed. Depending on the desired concentration, heat treatments at different temperatures of 800 ° C. and 1000 ° C. may be appropriately combined. Note that if the heat treatment time is shortened, the spread of the impurity distribution in the detection portion in the in-plane direction can be suppressed.
Thereafter, the diffusion mask M is completely etched away (the silicon nitride film is hot phosphoric acid and the silicon oxide film is hydrofluoric acid). The diffusion mask M, which is a thermal oxide film, contains boron, and is preferably completely removed after being used as an impurity diffusion mask. This is because if the diffusion mask M is left and used as an insulating layer as it is, re-diffusion of impurities occurs in a manufacturing process (particularly a process that requires heating) to be described later.

  Since the impurity distribution of the detection part spreads in the in-plane direction, current leakage occurs between the detection parts when the adjacent detection parts R are arranged too close to each other. Therefore, the detection parts R are arranged apart from each other by a distance larger than 6 μm. Further, the separation distance of the detection unit R is preferably less than ½ of the width of the flexible unit 123. This is because the detection unit R detects an output (so-called other-axis sensitivity) due to twisting that is not desired to be detected as the detection unit R is too far away from the center line of the flexible unit 123. The detection unit R is preferably arranged close to the center line of the flexible unit 123 in order to suppress twisting (so-called other-axis sensitivity) in a direction that is not desired to be detected.

(B) Vapor phase diffusion method Vapor phase diffusion is performed by exposing a gas containing B, P, etc. to a Si substrate. When diffusing B, a dopant gas such as BBr ₃ (sometimes O ₂ is allowed to flow together) is exposed to the opening in a diffusion furnace at a temperature of 750 ° C. to 900 ° C. to diffuse the dopant (impurities). Thereafter, a high concentration gas component on the surface is removed with an acid chemical solution such as hydrofluoric acid, and the surface is oxidized at a temperature of about 800 ° C. to form silicide. After removing the silicidized portion with an acid chemical solution such as hydrofluoric acid, heat treatment is performed at about 1000 ° C. to adjust the impurity concentration to a predetermined concentration of 10 ¹⁷ to 10 ¹⁹ (atoms / cm ³ ). . Depending on the desired concentration, heat treatments at different temperatures of 800 ° C. and 1000 ° C. may be appropriately combined. Note that if the heat treatment time is shortened, the spread of the impurity distribution in the detection portion in the in-plane direction can be suppressed.
According to the thermal diffusion method described above, since the ion implantation method is not used, no crystal defects are generated in the silicon film 120 constituting the flexible portion 123, and the physical quantity sensor manufactured using the thermal diffusion method has long-term stability. Have.

(4) Formation of insulating layer and contact hole (see FIG. 7D)
An insulating layer 150 is formed on the silicon film 120. The insulating layer 150 may be formed by a plasma CVD method or a low pressure CVD method. For example, a SiO ₂ layer is formed on the surface of the silicon film 120 by plasma CVD. Examples of film formation by plasma CVD are shown below. SiO ₂ may be a gas such as TEOS (Si (OC ₂ H ₅ ) ₄ ) / O ₂ , SiH ₄ / N ₂ O, the stress range is −200 MPa to +200 MPa, and the film thickness is in the range of 30 nm to 1 μm. If it exists, it is preferable at the point which can reduce influence on the sensitivity and offset voltage of a sensor. A contact hole 151 is formed on the insulating layer 150 by RIE using a resist as a mask. By newly forming the insulating layer 150 by a plasma CVD method, the insulating layer 150 free from impurity contamination can be formed. Note that the film stress is a value calculated by optically measuring the amount of warpage change of the filmed wafer (for example, the amount of change in the warpage (curvature radius) of the substrate before and after film formation was measured using a laser beam. The value obtained by arithmetic conversion of the value can be used as the film stress value).
Although the insulating layer 150 can be formed by thermally oxidizing the surface of the silicon film 120, it is not preferable because it induces diffusion of impurities when heat-treated.
Further, PSG (Phosphorus silicate glass) may be stacked on the insulating layer 150. The PSG film has a mobile ion gettering effect.

(5) Creation of wiring (refer to FIG. 7E)
A wiring 152 is formed. The wiring 152 is obtained by forming a metal material such as Al, Al—Si, or Al—Nd by sputtering or the like and patterning it. In addition, in order to form an ohmic contact between the wiring 152 and the detection unit R, heat treatment (380 ° C. to 420 ° C.) is performed. Note that a film such as a silicon nitride film (Si ₃ N ₄ ) may be provided over the wiring 152 as a protective film.

(6) Processing of silicon film (see FIG. 7F)
The silicon film 120 is etched by RIE or the like until the upper surface of the silicon oxide film 130 is exposed to form an opening 124, thereby defining the frame portion 121, the weight junction portion 122, and the flexible portion 123.

(7) Gap formation (see FIG. 7G)
The gap 160 is formed by etching the silicon substrate 140 using a mask having an opening along the inner frame of the frame portion 141. The gap 160 is an interval necessary for the weight portion 142 to be displaced downward (on the glass substrate 3 side), and is, for example, 5 to 10 μm.

(8) Processing of silicon substrate (see FIG. 7H)
Next, a mask for defining the frame part 141 and the weight part 142 is formed on the lower surface of the silicon substrate 140. Using this mask, the silicon substrate 140 is etched until the lower surface of the silicon oxide film 130 is exposed. It is preferable to use DRIE (Deep Reactive Ion Etching) for the etching.

In DRIE, an etching step of digging while eroding the material layer in the thickness direction and a deposition step of forming a polymer wall on the side wall of the carved hole are alternately repeated. Since the side wall of the hole that has been dug is protected by forming a polymer wall in sequence, it is possible to advance erosion almost only in the thickness direction. An ion / radical supply gas such as SF ₆ can be used as an etching gas, and C ₄ F ₈ or the like can be used as a deposition gas.

(9) Removal of unnecessary silicon oxide film (see FIG. 7I)
The unnecessary silicon oxide film used as an etching stopper is removed by RIE, wet etching, vapor hydrofluoric acid treatment, or the like. Thus, the silicon oxide film 130 exists between the frame portion 121 and the frame portion 141, and the weight joint portion 122 and the weight portion 142.

(10) Glass substrate bonding (see FIG. 7J)
The sensor body 2 and the glass substrate 3 are joined. The glass substrate 3 is so-called Pyrex (registered trademark) glass containing movable ions such as Na ions, and anodic bonding is used for bonding to the SOI substrate 110. In order to prevent the weight 142 from sticking to the upper surface of the glass substrate 3 due to electrostatic attraction during anodic bonding, a sticking prevention film (not shown) such as Cr is formed on the upper surface of the glass substrate 3 by sputtering. You may keep it. Thereby, the sensor main body 2 and the glass substrate 3 are joined, and the acceleration sensor 1 is comprised.

(11) Individualization The acceleration sensor 1 is diced with a dicing saw or the like, and is divided into individual acceleration sensors 1. In the present specification, the “acceleration sensor” arranged in a multi-face manner on the wafer and the “acceleration sensor” separated into pieces are referred to as the acceleration sensor 1 without any particular distinction. As described above, using the semiconductor substrate, the frame portion located on the outer peripheral portion, the weight portion disposed inside the frame portion, and the flexible portion having a smaller thickness than the frame portion, and connecting the frame portion and the weight portion. And a method of manufacturing an acceleration sensor that includes a plurality of piezoresistive elements that are formed in the flexible portion and detect physical quantity fluctuations.

(Second Embodiment)
A second embodiment will be described with reference to FIG. Except for the point that the groove 170 is formed between the detection parts R, it is substantially the same as the first embodiment. FIG. 5 is a diagram showing a second embodiment.
FIG. 5A is a top view of the flexible portion 123, and a groove portion 170 indicated by a hatched region is formed between the plurality of detection portions R. FIG. FIG. 5B illustrates a cross section of the flexible portion 123 along ZZ in FIG. By forming at least one groove 170 between the detection parts R, it is possible to achieve element isolation of the detection parts. The impurity diffusion region extends to some extent over the outer edge region of the detection portion R. Therefore, the impurity diffusion regions can be prevented from overlapping by the groove 170. Note that this embodiment is effective because the impurity diffusion region is widened even in a piezoresistive element formed by using the ion implantation method. By forming the groove part 170 between the detection parts, this embodiment can prevent current leakage due to the overlap of impurity diffusion regions between the detection parts, which is preferable. The groove part 170 may be formed not only between the detection parts but also around the detection part in a range where the strength of the flexible part 123 is not impaired. The groove 170 is formed by etching the silicon film 120 and digging it into several μm. The groove 170 is preferably formed deeper than the impurity depth of the piezoresistive element (depth of the impurity diffusion region in the substrate thickness direction) from the viewpoint of suppressing current leakage. For example, the depth of the groove is preferably 0.3 μm or more and 1/3 or less of the thickness of the silicon film 120. If the thickness is 0.3 μm or less, it is difficult to obtain the effect of suppressing current leakage, and if the thickness is larger than 1/3 of the thickness of the silicon film 120, the strength of the flexible portion 123 is lowered.

(Modification)
A modification of the first and second embodiments will be described with reference to FIG. 6 (Modification 1 to Modification 2).
§Modification 1
The detection unit R for detecting acceleration in the X, Y, and Z directions is configured by connecting a plurality of pairs of piezoresistive elements in series, and each piezoresistive element for detecting each direction is the center line of the flexible portion 123. Are arranged symmetrically. With the above configuration, when a twist that is not to be detected occurs when the piezoresistive element is arranged symmetrically with respect to the center line of the flexible portion 123, a reverse stress is applied to the piezoresistive element. Therefore, the influence of stress can be offset. Since the influence of other axis sensitivity can be suppressed, detection accuracy can be improved. Further, a sensor that achieves both high sensitivity and low power consumption can be provided by arranging short piezoresistive elements in the stress concentration portion and connecting them in series to increase the resistance length. As will be described later, it is preferable that the distance L ₁ between adjacent piezoresistive elements is larger than 6 μm in that the leak current value between the piezoresistive elements is small.

§Modification 2
A detection portion R for detecting acceleration in the X, Y, and Z directions is configured by a piezoresistive element having a folded shape and disposed in the flexible portion 123. A sensor that achieves both high sensitivity and low power consumption can be provided by arranging a piezoresistive element in a stress concentration portion and integrally forming a folded shape to increase the resistance length. As will be described later, it is preferable that the distance L ₁ between adjacent piezoresistive element portions is larger than 6 μm in that the leak current value between the piezoresistive elements is small.

Hereinafter, for the physical quantity sensor (piezoresistive acceleration sensor) according to the first embodiment, the leakage current value between Rx and Rz when the distance between the detection units was changed was measured. The leakage current value was measured by applying a voltage between Rx and Rz and measuring the current value flowing between the detection parts. FIG. 8 is a diagram illustrating the relationship between the distance between the detection units and the leakage current. The piezoresistive element was formed by a thermal diffusion method so that the surface concentration of impurities was about 3.2 × 10 ¹⁷ atoms / cm ³ and the impurity diffusion depth was 1.5 μm. When the distance between the detection units was larger than 6 μm, the leakage current between the detection units was very small when the applied voltage was in the range of 0V to 10V. It was confirmed that the leakage current was smaller than a predetermined value when the distance between the detection units was 7 μm, 8 μm, 10 μm, 12 μm, 15 μm, and 30 μm. On the other hand, when the distance between the plurality of detection units was 6 μm or less (the mutual distance was 5 μm or 6 μm), the leakage current between the detection units was measured.

  As described above, the embodiments of the present invention are not limited to the above-described embodiments, and can be expanded and modified. The expanded and modified embodiments are also included in the technical scope of the present invention.

1 is an overall perspective view of an acceleration sensor according to the present invention. It is a disassembled perspective view of an acceleration sensor. It is the top view and sectional drawing of a sensor main body. 1 is a diagram illustrating a first embodiment according to the present invention. It is drawing showing 2nd Embodiment which concerns on this invention. It is drawing showing the modification of this invention. It is drawing showing the manufacturing method of 1st Embodiment which concerns on this invention. It is drawing which shows the relationship between the distance between detection parts, and leakage current.

Explanation of symbols

1: Acceleration sensor 2: Sensor body 3: Support substrate 110: SOI substrate 120: Silicon film 121: Frame portion 122: Weight joint portion 123: Flexible portion 124: Opening 130: Silicon oxide film 140: Silicon substrate 141: Frame portion 142: weight part 150: insulating layer 151: contact hole 152: wiring 160: gap 170: groove part

R: detector (piezoresistive element)
Rx1 to Rx4: detecting units Ry2 to Ry4 (for detecting acceleration in the X-axis direction): detecting units Rz1 to Rz4 (for detecting acceleration in the Y-axis direction): (for detecting acceleration in the Z-axis direction) Detection unit M: diffusion mask

Claims (6)

Forming a mask having an opening on a semiconductor substrate;
Forming a plurality of piezoresistive elements on the semiconductor substrate exposed by the opening by a thermal diffusion method;
Removing the mask after forming the piezoresistive element;
Forming an insulating layer covering at least a part of the piezoresistive element on the semiconductor substrate;
Forming a contact hole by opening the insulating layer in a formation region of the piezoresistive element;
The manufacturing method of the physical quantity sensor characterized by including.   2. The method of manufacturing a physical quantity sensor according to claim 1, wherein a distance between the plurality of piezoresistive elements is set to be larger than 6 [mu] m.   The method of manufacturing a physical quantity sensor according to claim 1, further comprising a step of forming a groove between the plurality of piezoresistive elements.   The method of manufacturing a physical quantity sensor according to claim 1, wherein the insulating layer is formed by a CVD method. A frame portion located on the outer periphery,
A weight portion disposed inside the frame portion;
A flexible part that connects the frame part and the weight part and is thinner than the frame part;
A plurality of piezoresistive elements formed on the flexible portion for detecting physical quantity fluctuations,
A physical quantity sensor characterized in that a distance between the plurality of piezoresistive elements is larger than 6 μm.   The physical quantity sensor according to claim 5, further comprising a groove between the piezoresistive elements.

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